The present application claims priority under 35 U.S.C. xc2xa7119 of German Patent Application No. 101 02 199.2, filed Jan. 18, 2001, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The invention relates to a process for conditioning a circulating felt belt of a machine, in particular a paper machine, used to produce a fibrous material web, in particular a paper or cardboard web.
A corresponding treatment or conditioning of felt belts can serve, for example, to improve the profile quality of felt and paper, to improve the web running properties, and possibly also an increase in the stability of the dewatering and/or the dry matter content, etc.
2. Discussion of Background Information
At least one pressing felt is generally used for pressing the paper web for the purpose of increasing the dry matter content. In order to achieve an even as possible increase of the dry matter content crosswise to the machine direction, i.e., an even moisture cross direction profile, various felt conditioning devices are used. As a rule, these devices comprise a device for drawing water into the felt and a subsequent device that suctions out of the felt the water that has been drawn into it.
In spite of such a felt conditioning, an uneven loading of the felt with contaminants and an uneven compression of the felt occur during the service life of the felt, which leads to an uneven dewatering in the pressing nip. Up to now, a correction of the resulting uneven moisture cross direction profile has been performed by means of a zonal temperature increase in the press nip by applying water steam to the paper web. However, this does not eliminate the causes of the unevenness in the condition of the felt.
In a paper machine known from U.S. Pat. No. 4,378,639, the fibrous material web is constantly monitored for dry streaks in the drying section and the web is correspondingly moistened depending on the results of the monitoring. In a conditioning process known from DE-A-44 19 540, various methods are used for conditioning felt belts. Paper machines are also already known in which the respective state of a felt is monitored in order to be able to perform the conditioning of the felt depending on the detected condition of the felt (cf., for example, EP-A-0 383 486, EP-A-0 024 205). In a paper machine known from DE-A-198 60 567, the conditioning of each transport belt occurs depending on the contamination of this transport belt that is detected.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.
One aspect of the invention resides in further developing the process of the type mentioned at the outset in such a way that the moisture cross direction profile can be optimally corrected in order to attain an even moisture cross direction profile, in particular.
In order to attain this goal, a process is recommended according to the invention for conditioning a circulating felt belt of a machine, in particular a paper machine, used to produce a fibrous material web, in particular a paper or cardboard web, in which a conditioning is performed in zones across the felt belt width, in that at least one fibrous material web property cross profile and/or at least one felt belt property cross profile such as, in particular, the water content of the felt belt across the width of the web and/or the belt and/or the permeability of the felt belt across the width of the web and/or the belt is measured and the felt belt is conditioned in each of the various zones depending on the measuring results obtained for the applicable zones.
The zonal conditioning can, for example, occur in addition to a conditioning that is effective across the entire belt width. However, this is not obligatory in any case.
Thus, for example, it is possible in particular to correct deviations in the moisture cross direction profile and to achieve an even moisture cross direction profile by means of a targeted treatment or conditioning of the felt in places where deviations of the felt properties from the desired values occur and, e.g., a particularly high degree of compression or contamination, a deviation from the desired water content and/or the like is present. Here, it is possible, for example, to apply water at compressed places in the felt and/or to suction water off at compressed points in the felt or to blow water out using pressurized air, using a spraying pipe, for example, a high-pressure spraying pipe.
According to a suitable practical design of the process according to the invention, a mean value is calculated from measured values obtained for the various zones and the intensity of the conditioning in a respective zone is selected depending on the deviation of the measured result from the mean value.
It is possible, for example, for the following devices to be used individually or in any desired combination with one another for the purpose of zonal felt conditioning.
Thus, the felt conditioning can occur at least partially, for example, by means of at least one traversing spraying pipe nozzle. Using an appropriate guide, it is thus possible to approach all points across the width of the felt. The nozzle can, e.g., either travel across the felt belt at an even speed, in which case the water pressure can be correspondingly regulated with the cross profile deviation as a correcting variable, or the speed of the nozzle and thus its lag time at various positions can be regulated, at a constant water pressure, with the cross profile deviation as a correcting variable.
Alternatively or additionally, the felt conditioning can at least partially occur also by means of at least one spraying pipe comprising several nozzles, which can be controlled zonally and can also preferably be moved over the width of the zone. For a targeted conditioning of individual felt areas, the individual spraying pipe nozzles can each be controlled by the relevant valves.
Alternatively or additionally, the felt conditioning can at least partially occur also by means of a zonally controllable pipe suction apparatus that is additionally preferably movable over the width of the zone. Using such a pipe suction apparatus, individual regions of the felt can be suctioned in a targeted manner.
A pipe suction apparatus can be used, for example, that has a ceramic body extending at least essentially over the entire width of the felt, which ceramic body is provided with a slotted surface by way of which the felt belt can be subjected to vacuum, with the effective slotted portion of the surface being variably adjustable by zones, in particular using movable tongues, e.g., metal tongues in order to correspondingly vary, in particular, the respective effective time of the vacuum.
However, the felt conditioning can, for example, also occur at least partially by means of at least one traversing short pipe suction apparatus that has a ceramic body that is provided with a slotted surface by way of which the felt belt can be subjected to vacuum, where the effective slotted portion of the surface may be variably adjusted by means of at least one movable tongue, e.g., a metal tongue, in order to correspondingly vary, in particular, the respective effective time of the vacuum.
Further examples of possibilities for treating and/or conditioning the felt are as follows:
Pressurized air for blowing out water, e.g., regulation of the water content
Chemical conditioning additives, profiling by means of amount and/or dosing, e.g., regulation of the permeability
All types of treatment and/or conditioning are possible on the paper side and/or the running side.
The significance of even moisture cross direction profiles after a pressing section is a deciding factor for the degree of effectiveness and the quality of the final product. If, for example, moist areas occur, the strength of the web is reduced at that point, which is connected with a significantly greater tendency to tear. For example, altered tension requirements in the drying section and the adjustment of the tension in the drying section after the most moist area should be mentioned; it should be taken into account here that too great of a tension at dry areas can, in particular, lead to the formation of creases. Moreover, a complete evening out of the moisture cross direction profile in the drying section is not possible in many cases. If the paper machine includes a calender, moist areas have a considerable influence on the quality properties of gloss and smoothness that can be achieved with the calender.
In many cases, uneven felt properties such as, in particular, an uneven permeability and an uneven water content, are the causes of irregularities in the moisture cross direction profile.
Conventional presses have exclusively conditioning devices acting evenly across their width such as, in particular, low-pressure and high-pressure spraying pipes and DuoCleaner.
Web running problems in connection with the felt conditioning are, for example:
Edge pulling during felt separation. In other words, in felt separation after double felt presses, the edge of the paper web is removed in places from the felt guiding the paper by the removed felt.
Edge lifting and/or edge folding. The edges of the paper do not have sufficient adhesion on the felt and/or the necessary difference between the upper felt and the lower felt is not sufficient.
These irregularities can be caused by the surface properties of the felts. The properties in question are determined by the fleece properties/refinements and by the conditioning.
The properties in question are dependent less on the type of conditioning and/or treatment than on the requirements of the different or adapted application of the treatment.
Therefore, there are various options for felt treatment, including treatment in sections for improving the profile qualities of the felt and the paper web.
A further aspect of the invention is therefore, in particular, the guarantee of good web running properties. Certain properties across the width of the felt, especially in the edge regions, must be taken into account. Moreover, differences between the upper felt and the lower felt should be eliminated. In other words, the profile correction can only move within a working window that is determined by the web running requirements. Web running properties are, in particular, the surface affinity of felt and paper and the permeability of the felt for the effect of vacuum on the web. The process of the type mentioned at the outset should, moreover, be further developed in such a way that an improvement in the moisture cross direction profile is attained and the danger of so-called edge pulling is reduced.
In order to attain this goal, a process is recommended according to the invention for conditioning a circulating felt belt of a machine, in particular a paper machine, used to produce a fibrous material web, in particular a paper or cardboard web, in which a zonal conditioning is performed across the width of the felt belt in that the amounts of the conditioning medium added at the various zones are separately adjusted in accordance with the respective, in particular variable, target values.
Thus, the problems mentioned above are eliminated. For example, the effectiveness of the above-mentioned conditioning devices across the width of the felt can optionally also be different, whereby the cross profiles can be correspondingly improved and the danger of a so-called edge pulling can be correspondingly reduced. Good web running properties are guaranteed. Certain properties across the width of the felt, especially in particular in the edge areas, can be correspondingly taken into account and differences between the upper felt and the lower felt can be eliminated. In other words, the profile correction can move only in a working window that is determined by the web running requirements. Web running properties are, in particular, the surface affinity of felt and paper and the permeability of the felt for the effect of vacuum on the web. An improvement in the moisture cross direction profile is attained and the danger of so-called edge pulling is reduced. In general, a more optimal adaptation is possible.
The dosing of conditioning medium, which may optionally differ, across the width of the felt belt can occur in various ways.
According to an advantageous practical embodiment, the conditioning medium is preferably diluted uniformly outside the machine.
If the introduction of conditioning medium occurs at least partially by means of at least one traversing application unit, then the amount of conditioning medium determined for each zone is preferably set using the lag time of the traversing application unit in the respective zone.
If the introduction of conditioning medium occurs at least partially by means of a plurality of stationary nozzles arranged across the width of the felt, to which nozzles a corresponding number of valves is assigned, then the amount of conditioning medium determined for each zone is preferably set by means of a respective valve assigned to the nozzle in question.
According to a suitable practical embodiment of the process according to the invention, the conditioning medium, which preferably contains conditioning chemicals, is mixed into the conditioning water.
According to another advantageous embodiment, the conditioning medium, preferably conditioning chemicals, can be supplied to at least one application device provided especially for chemical conditioning.
It is also advantageous for a preferably zonal regulation of the amount of conditioning medium supplied to be provided.
Further possibilities for treating and/or conditioning the felt are as follows, for example:
Pressurized air for blowing out water, e.g., regulation of the water content
Chemical conditioning additives, profiling by means of amount and/or dosing, e.g., regulation of the permeability
All methods of treatment and/or conditioning are possible on the paper side and/or the running side.
Felt properties, for example, water content or permeability, change with their running time, sometimes also unevenly across the felt width, whereby the moisture cross direction profile of the paper web can be negatively influenced. Moreover, as a result the runnability of the paper web can also be negatively influenced (web edge problems). Reference is again made by way of example to the above-mentioned web running problems and the like occurring in connection with the felt conditioning.
A further aspect of the invention is therefore to further develop the process of the type mentioned at the outset in such a way that, in order to achieve an optimal dry matter content with a good moisture cross direction profile after the press, even and targeted felt properties are guaranteed across the width of the felt belt and a good web run can be guaranteed by virtue of targeted felt properties.
In order to attain this goal, a process for conditioning a circulating felt belt of a machine, in particular a paper machine, used to produce a fibrous material web, in particular a paper or cardboard web, is recommended according to the invention in which a zonal conditioning is performed across the width of the felt belt in that at least one felt belt property cross profile is measured and zonal conditioning elements across the width of the felt belt are adjusted to correspond to the measured felt belt property cross profile.
Here, in particular, an adjustment of zonal or sectional conditioning elements provided across the width of the felt belt corresponding to the felt belt property cross profiles (for example, pressure HD-SR↑, vacuum RS↓ at dry points on the felt) is possible.
According to an advantageous embodiment of the process according to the invention, the felt belt property cross profile is measured by means of an online measurement device, with a closed-loop control preferably being formed in connection with each of the zonal conditioning elements.
In certain cases, it is advantageous for at least one predeterminable felt property mean value and/or at least one predeterminable ratio of a felt property mean value for an upper felt and a lower felt to be adjusted. Here, the respective felt property mean value and/or the respective ratio of felt property mean values for the upper and lower felt of a double-felted pressing nip can be adjusted for the purpose of achieving an optimal dry matter content and an optimal moisture cross direction profile after the nip and/or after the pressing section with optimal web running.
It is also advantageous for the moisture cross direction profile and/or the dewatering amounts occurring in grooves and/or pipe suction apparatus to be measured online immediately after the pressing section and for the zonal conditioning elements to be adjusted depending upon the measuring results attained thereby.
Thus, for example, the online measurement of the moisture cross direction profile directly after the pressing section, in particular in conjunction with the above-mentioned measures and optionally including the measured dewatering amounts at the grooves and pipe suction apparatuses in question, which preferably occurs online as well, allows a complex regulation cycle for achieving an optimal dry matter content and an optimal moisture cross direction profile after the press and an optimal web running; this complex regulation cycle could also possibly be constructed in a self-learning manner.
The invention further relates to a pipe suction apparatus for conditioning a circulating felt belt that is suitable in a particular way for performing the process according to the invention.
According to a first variant embodiment, the pipe suction apparatus according to the invention is provided with a ceramic body extending at least essentially across the entire width of the felt, which ceramic body is provided with a slotted surface, by way of which the felt belt may be subjected to vacuum, with the respective effective amount of slotted surface being variably adjustable by means of movable tongues, e.g., metal tongues, for the purpose of, in particular, correspondingly varying the respective effective time of the vacuum.
According to another variant embodiment of the invention, a traversing pipe suction apparatus is provided for conditioning a circulating felt belt having a ceramic body that is provided with a slotted surface by way of which the felt belt can be subjected to vacuum, with the effect amount of slotted surface is variably adjustable, in particular by means of at least one movable tongue, e.g., metal tongues, for the purpose of, in particular, correspondingly varying the respective effective time of the vacuum.
According to the invention, the process for conditioning a circulating felt belt of a machine for producing a fibrous material web, comprises performing a zonal conditioning of a plurality of zones across a width of the felt belt by measuring at least one of: fibrous material web cross direction profile; felt belt cross direction profile; and permeability of the felt belt across the width of at least one of the web and the belt, and further comprises conditioning the felt belt depending on measuring results obtained for a respective zone. The machine may comprise a paper making machine. The fibrous material web may comprise one of a paper or cardboard web. The fibrous material web cross direction profile may comprise a moisture cross direction profile of the fibrous material web. The felt belt cross direction profile may comprise a water content of the felt belt across the width of at least one of the web and the belt.
According to another aspect of the invention, the process further comprises calculating a mean value from the measured values obtained for the various zones and selecting the intensity of the conditioning in each zone depending upon the deviation of the measuring results obtained for the respective zone from the mean value.
The felt conditioning may occur at least partially by way of a traversing spraying nozzle. Alternatively, the felt conditioning may occur at least partially by way of at least one spraying pipe that includes several nozzles. The at least one spraying pipe may be zonally controllable. The process may further comprise moving the at least one spraying pipe across the width of the zones. Alternatively, the felt conditioning may occur at least partially by way of at least one pipe suction apparatus. The at least one pipe suction apparatus may be zonally controllable.
The process, according to a further aspect of the invention, comprises moving the at least one pipe suction apparatus across a width of the zones. The pipe suction apparatus includes a ceramic body extending at least essentially across the entire width of the felt belt, and the process further comprises subjecting the felt belt to vacuum by way of a slotted surface formed in the ceramic body, and variably adjusting, by zones, an effective slotted portion of the surface, to vary, a respective effective time of being subjected to vacuum.
The process, according to the invention, further comprises variably adjusting, by way of movable tongues, an effective slotted portion of the surface. The movable tongues may comprise metal tongues.
The felt conditioning may occur at least partially by way of at least one traversing short pipe suction apparatus including a ceramic body provided with a slotted surface by way of which the felt belt is subjectable to vacuum, and further by variably adjusting by zones, an effective slotted portion of the surface to vary a respective effective time of being subjected to vacuum. An effective slotted portion of the surface may be variably adjustable by using movable tongues. The movable tongues may comprise metal tongues.
The zonal conditioning comprises supplying separately adjustable amounts of conditioning medium to various zones in accordance with respective target values, which may be variable. The conditioning medium may be diluted outside of the machine. The supplying of conditioning medium may occur at least partially by way of at least one traversing application unit, and determining the amount of conditioning medium supplied to each zone by using a lag time of the traversing application unit in the respective zone.
According to an alternative aspect of the invention, the supplying of conditioning medium occurs at least partially by way of a plurality of stationary nozzles provided across the width of the felt belt, with a corresponding number of valves being assigned to the nozzles, and the amount of conditioning medium supplied being determined for each zone by way of a respective valve assigned to the relevant nozzle. The zonal conditioning may comprise supplying conditioning medium across a width of the felt belt. The conditioning medium may comprise conditioning chemicals mixed into conditioning water. Further, the conditioning medium may comprise conditioning chemicals supplied to at least one conditioning device provided only for chemical conditioning.
The invention further comprises providing a zonal regulation of the supplied conditioning medium and measuring at least one felt belt cross direction profile and adjusting zonal conditioning elements across the width of the felt belt according to the measured felt belt cross direction profile.
The felt belt cross direction profile is measured by way of an online measuring device, with a closed-loop control preferably being formed in connection with each of the zonal conditioning elements. The invention further comprises setting at least one of predeterminable felt mean value and predeterminable ratio of a felt mean value for at least one of an upper felt and a lower felt.
Another aspect of the invention includes setting the at least one of predeterminable felt mean value and predeterminable ratio of a felt mean value, depending on at least one of a desired dry matter content and moisture cross direction profile after a respective at least one of a pressing nip and a press section. A further aspect of the invention includes measuring online, immediately after the press section, at least one of a moisture cross direction profile and dewatering amounts occurring at at least one of grooves and pipe suction apparatus and adjusting the zonal conditioning elements depending on the measuring result that is obtained therefrom.
Moreover, according to the invention, there is provided a pipe suction apparatus for conditioning a circulating felt belt, wherein a zonal conditioning of a plurality of zones across a width of the felt belt is performed by measuring at least one of fibrous material web cross direction profile; felt belt cross direction profile; and permeability of the felt belt across the width of at least one of the web and the belt; and further comprising conditioning the felt belt depending on measuring results obtained for a respective zone, wherein the apparatus comprises a ceramic body extending at least essentially across the entire width of the felt belt, the ceramic body being provided with a slotted surface by way of which the felt belt is subjectable to vacuum, with a respective effective amount of slotted surface being zonally variably adjustable by way of movable tongues.
The movable tongues may comprise metal tongues. A respective effective time of being subjected to vacuum is correspondingly varied.
According to yet another aspect of the invention, a traversing pipe suction apparatus for conditioning a circulating felt belt, includes a zonal conditioning of a plurality of zones across a width of the felt belt performed by measuring at least one of fibrous material web cross direction profile; felt belt cross direction profile; and permeability of the felt belt across the width of at least one of the web and the belt, and further includes conditioning the felt belt depending on measuring results obtained for a respective zone, wherein the apparatus comprises a ceramic body provided with a slotted surface by way of which the felt belt is subjectable to vacuum, with an effective amount of slotted surface being variably adjustable by way of at least one movable tongue. The movable tongue may comprises a metal tongue. A respective effective time of being subjected to vacuum is correspondingly varied.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.